how hash_t toHash() works?

[gedaiu]

On Monday, 29 April 2013 at 16:01:15 UTC, Ivan Kazmenko wrote:
>> one more question
>> What is the type of cont?
>>
>> auto cont = redBlackTree !("a.key < b.key", true, MyRecord) ();
>>
>> I want to use this as a property in a class and i can't use 
>> there auto keyword... I tried different types but it did not 
>> work.
>
> For me, the following declaration works:
>
> -----
> import std.functional;
> ...
> 	RedBlackTree !(MyRecord, binaryFun!"a.key < b.key", true) cont;
> ...
> 	cont = redBlackTree !("a.key < b.key", true, MyRecord) ();
> -----
>
> I admit it could have been easier to figure out.  For example, 
> "writeln (typeof (cont).stringof);" just prints "RedBlackTree" 
> which is not enough for a proper declaration.  I've inferred 
> the right declaration from the following lines in container.d:
>
> -----
> /++ Ditto +/
> auto redBlackTree(alias less, bool allowDuplicates, E)(E[] 
> elems...)
>     if(is(typeof(binaryFun!less(E.init, E.init))))
> {
>     //We shouldn't need to instantiate less here, but for some 
> reason,
>     //dmd can't handle it if we don't (even though the template 
> which
>     //takes less but not allowDuplicates works just fine).
>     return new RedBlackTree!(E, binaryFun!less, 
> allowDuplicates)(elems);
> }
> -----

Error: template instance RedBlackTree!(ValueRecord, binaryFun, 
true) RedBlackTree!(ValueRecord, binaryFun, true) does not match 
template declaration RedBlackTree(T, alias less = "a < b", bool 
allowDuplicates = false) if (is(typeof(binaryFun!(less)(T.init, 
T.init))))
Error: RedBlackTree!(ValueRecord, binaryFun, true) is used as a 
type

Do you know what this error means?

Thank,
Bogdan